Make nodes comparable

Author: David Ungar

Sources/SwiftDriver/Incremental Compilation/DependencyKey.swift

@@ -2,7 +2,7 @@
 import Foundation
 
 /// A filename from another module
-struct ExternalDependency: Hashable, CustomStringConvertible {
+struct ExternalDependency: Hashable, Comparable, CustomStringConvertible {
   let fileName: String
 
   var file: VirtualPath? {
@@ -14,6 +14,10 @@ struct ExternalDependency: Hashable, CustomStringConvertible {
   public var description: String {
     fileName.description
   }
+
+  public static func < (lhs: Self, rhs: Self) -> Bool {
+    lhs.fileName < rhs.fileName
+  }
 }
 
 
@@ -31,7 +35,7 @@ public struct DependencyKey: Hashable, CustomStringConvertible {
   /// implementations white. Each node holds an instance variable describing which
   /// aspect of the entity it represents.
 
-  enum DeclAspect {
+  enum DeclAspect: Comparable {
     case interface, implementation
   }
 
@@ -112,3 +116,15 @@ var correspondingImplementation: Self? {
   }
 }
 
+// MARK: - Comparing
+/// Needed to sort nodes to make tracing deterministic to test against emitted diagnostics
+extension DependencyKey: Comparable {
+  public static func < (lhs: Self, rhs: Self) -> Bool {
+    lhs.aspect != rhs.aspect ? lhs.aspect < rhs.aspect :
+      lhs.designator < rhs.designator
+  }
+}
+
+extension DependencyKey.Designator: Comparable {
+}
+

Sources/SwiftDriver/Incremental Compilation/ModuleDependencyGraph Parts/Node.swift

@@ -80,6 +80,22 @@ extension ModuleDependencyGraph.Node: Equatable, Hashable {
   }
 }
 
+extension ModuleDependencyGraph.Node: Comparable {
+  static func < (lhs: ModuleDependencyGraph.Node, rhs: ModuleDependencyGraph.Node) -> Bool {
+    func lt<T: Comparable> (_ a: T?, _ b: T?) -> Bool {
+      switch (a, b) {
+      case let (x?, y?): return x < y
+      case (nil, nil): return false
+      case (nil, _?): return true
+      case (_?, nil): return false
+      }
+    }
+    return lhs.dependencyKey != rhs.dependencyKey ? lhs.dependencyKey < rhs.dependencyKey :
+      lhs.swiftDeps != rhs.swiftDeps ? lt(lhs.swiftDeps, rhs.swiftDeps)
+      : lt(lhs.fingerprint, rhs.fingerprint)
+  }
+}
+
 
 extension ModuleDependencyGraph.Node: CustomStringConvertible {
   public var description: String {

Sources/SwiftDriver/Incremental Compilation/ModuleDependencyGraph Parts/SwiftDeps.swift

@@ -46,3 +46,9 @@ extension ModuleDependencyGraph.SwiftDeps {
     file.name
   }
 }
+// MARK: - comparing
+extension ModuleDependencyGraph.SwiftDeps: Comparable {
+  static func < (lhs: Self, rhs: Self) -> Bool {
+    lhs.file.name < rhs.file.name
+  }
+}